Surgery for removal of intrinsic brain tumors can lead to unintended cognitive impairments. This is particularly the case when healthy tissue must be resected (corticectomy) in order to access the tumor. The consequences of corticectomy for neural function and cognitive outcome remain poorly understood. Recent advances in studying dynamic interactions among brain regions using functional magnetic resonance imaging (fMRI) data collected while subjects are at rest, with no overt stimulus or task, open up new horizons for studying the neural consequences of radical resection of intrinsic brain tumors. This imaging modality is well suited for application and development within a clinical setting, as data may be collected from patients of heterogeneous cognitive abilities as part of their standard clinical assessment. The ability to recognize and use objects according to their function (e.g., fork, hammer, pencil) requires coordinated processing across multiple brain regions in temporal and parietal cortex. Those cognitive abilities can be compromised after neurosurgery for removal of temporal or parietal lobe brain tumors. The proposed research program uses resting fMRI to study the organization of the cortical networks supporting knowledge of common objects. Patients with brain tumors in the temporal and parietal lobes will be scanned with stimulus- based and resting fMRI and will undergo detailed neuropsychological testing before surgery and after surgery. Using regions of interest (ROIs) defined with stimulus-based fMRI, functional connectivity will be quantified within the temporal-parietal cortical network supporting object knowledge. On the basis of the PIs previous research, specific hypotheses are advanced about anticipated changes in connectivity as a function of the location of the brain tumor and the nature of the surgical approach for removal of the tumor. Those hypotheses are then tested by comparing the post-surgery data to the pre-surgery data, and relating changes in functional connectivity to changes in cognitive abilities. To this end, a new method is developed that applies the analytical tool of lesion-symptom mapping to fMRI connectivity maps in order to be able to derive whole brain maps showing how changes in functional connectivity are related to changes in cognitive performance. This research program serves two goals. First, it will generate a new type of feedback about patient outcome to neurosurgeons that will inform surgical planning in patients undergoing resection of intrinsic brain tumors. Second, hypotheses about the functional brain networks that support visual object identification and object use are tested, and causal inferences are drawn about the brain processes that subserve those complex behaviors.
Functional MRI is used to test hypotheses about plasticity in the cortical networks supporting object knowledge in neurosurgery patients with dominant hemisphere brain tumors. In addition to studying the constraints that shape brain organization, a prognostic metric will be developed for planning the location of corticectomies.
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